The present invention relates to a semiconductor component, in particular a transistor, such as a trench transistor, for example.
A trench transistor has a gate electrode arranged in at least one trench of a semiconductor body and serving for controlling a conducting channel in a body zone arranged between a source zone doped complementarily to the body zone and a drift zone doped complementarily to the body zone. The drift zone is arranged between the source zone and a drain zone, wherein the doping and the dimensions of the drift zone crucially determine the dielectric strength of the component.
In order to increase the dielectric strength a field electrode may be provided in the trench of the gate electrode, the field electrode being arranged adjacent to the drift zone and being at gate potential. When the component is turned off, the field electrode serves for compensation of part of the dopant charge present in the drift zone. In the known component, a plurality of trenches having gate electrode sections and field electrode sections arranged therein are present and arranged at a distance from the drain zone. In this case, a distance between the trench and the drain zone is intended to be approximately half as large as a mutual distance between two adjacent trenches.
In “dense trench” transistors gate electrode sections and field electrode sections are spaced apart so closely that during static operation, when a reverse voltage is applied, a field strength maximum occurs at a lower end of the trenches in the drift zone, such that an avalanche breakdown occurs in this region when the dielectric strength limit is exceeded. Transistors of this type are also referred to as “dense trench” transistors.
A further example of a trench transistor is described in DE 10 2004 052 678 B3.
In components of this type, a distinction can be made between two breakdown regimes: the static breakdown explained above, in which only a current having a low current density flows after the breakdown and which is referred to hereinafter as breakdown with low current density; and a breakdown with high current density, in which a high current density is established rapidly in a drift zone section arranged between the trenches. In the case of such a breakdown with high current density, in dense trench transistors the field strength maximum may no longer occur at the lower end of the trenches, but rather at a pn junction between the body zone and the drift zone. This is unfavorable because the entire avalanche current flowing through the component is concentrated on the mesa region between two trenches in which the avalanche breakdown first commences. This can lead to local damage to the component, whereby the component becomes unusable. During an avalanche breakdown that occurs below the trenches in the drift zone, by contrast, the avalanche current is distributed between a plurality of mesa regions, which reduces the risk of destruction.